The specifications of electrical products for consumers change with each passing day, and a trend for reducing sizes of mobile phones has not declined. As a result, the specifications of critical elements of optical lens must also be upgraded continuously to conform to consumers' demands. The most important characteristics of an optical lens may include its imaging quality and size. About an optical imaging lens comprising five lens elements, a distance between an object-side surface of a first lens element of the optical imaging lens and an imaging plane along an optical axis is longer, so goals of smaller sized mobile phones and digital cameras may not be achieved easily. Therefore, there is a need to develop an optical lens having improved imaging quality and shorter length.